(Received 20 February 2013;accepted 28 February 2013;online 6 March 2013)

The asymmetric unit of the title compound, C26H18N6O4S, contains two independent mol­ecules (A and B). The dihedral angles between the oxadiazole ring and naphthalene ring system are 42.59 (14) and 6.88 (14) Å in mol­ecules A and B, respectively. The dihedral angles between the pyridine and benzene rings in A and B are 65.53 (13 )and 87.67 (13) Å, respectively. In the crystal, mol­ecules A and B are linked through a pair of N—H⋯N hydrogen bonds involving one -NH2 group H atom and second pair of N—H⋯N hydrogen bonds involving the other -NH2 group H atom, forming an –ABAB– ribbon along [100] containing R22(8) and R22(12) ring motifs. These ribbons are further connected by weak C—H⋯N, C—H⋯O and C—H⋯π inter­actions, resulting in a three-dimensional network. The crystal studied was a non-merohedral twin with refined components 0.906 (1):0.094 (1).

The asymmetric unit of the title compound consists of two crystallographically independent, 5-(5-((naphthalen-6-yloxy)methyl)-1,3,4-oxadiazol-2-ylthio) -2-amino-6-methyl-4-(3-nitrophenyl)pyridine-3-carbonitrile molecules (A & B), as shown in Fig. 1. The bond lengths and angles of molecules A and B agree with each other and are within normal ranges for bond lengths (Allen et al., 1987). The dihedral angles between pyridine rings (N3A/C14A–C18A)/ (N3B/C14B–C18B) and the benzene rings (C19A–C24A)/(C19B–C24B) are 65.53 (13) and 87.67 (13) Å, respectively. The central 1,3,4-oxadiazole ring system in both the molecules is essentially planar with maximum deviations of 0.007 (3) and 0.002 (3) %A respectively.

In the crystal structure (Fig. 2), molecule A is paired with molecule B via an N4—H···N3ii hydrogen bonds (symmetry code in Table 1), involving the 4-amino group and the pyridine N1 atom and it is paired with another molecule of B through a pair N4—H···N5i hydrogen bonds (symmetry code in Table 1), involving the 4-amino group and cyano N5 atom, forming R22(8) and R22(12) (Bernstein et al., 1995) ring motifs. These hydrogen-bonded ABAB pairs lead to a extended ribbon structure. Theese ribbon are linked by weak C—H···N, C—H···O hydrogen bonds, resulting in a three-dimensional network. The crystal structure is further stabilized by C—H···π interactions (Table 1).

N-bound H atoms were located in a difference Fourier map and were refined freely [refined N–H distance 0.86 (4), 0.84 (4), 0.92 (4) and 0.85 (4) Å]. The remaining hydrogen atoms were positioned geometrically [C–H = 0.95–0.99 Å] and were refined using a riding model, with Uiso(H) = 1.2 Ueq(C) or 1.5Ueq(methyl C). A rotating-group model was used for the methyl group. The crystal used was a non-merohedral twin with refined components 0.906 (1):0.094 (1). The structure was refined using the HKLF 5 type input.

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

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